package h0710;

import java.util.Scanner;

public class WordWeight {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        String s = sc.nextLine();
        String[] split = s.split(" ");
        double sum=0;
        for (String string : split) {
            sum+=string.length();
        }
        double res=sum/split.length;
        //使用String.format,保留n位小数
        System.out.println(String.format("%.2f",res));
    }
}
